1. Field of the Invention
The present invention relates to an image rectification method and related device for a video device, and more particularly, to an image rectification method and related device for rectifying a received image according to a position of the received image shown in the video device.
2. Description of the Prior Art
Real-time text messages and VoIP phone are popular internet applications in modern life. With the advancement of internet technology, people are dissatisfied with pure text or voice communication, and therefore videoconferencing applications arise. People can make videoconference calls with real-time images, which brings many more interactive effects, to communicate with others. Communications are much more precise and interesting via videoconferencing applications.
In a common video device, such as a desktop computer or a laptop computer, a camera is usually set above a screen of the computer. A computer user, hereinafter call transmitter, views a facial image of another computer user, hereinafter called a receiver, shown in the screen, and the transmitter uses the camera to capture real-time images of the transmitter and transmits images to the receiver. Please refer to FIG. 1, which illustrates a relationship between video devices and the video device users. As shown in FIG. 1, a transmitter using a video device A makes a videoconference call to a receiver using a video device B. Note that there is a distance between a camera of the video device A and the facial image of the receiver shown in a screen of the video device A. Further, line of sight of the transmitter is toward the image of the receiver, not toward the camera, such that an angular deviation θ is formed between the line of sight of the transmitter and the direction from the transmitter's eyes to the camera.
In the viewpoint of the receiver, the receiver may feel that the transmitter is not looking at the receiver but is looking down with the angular deviation θ. Hence, the experience of the receiver using the videoconference application is affected. The receiver can receive an eye-to-eye image only when the transmitter is looking at the camera, whereas the transmitter may not know whether the receiver is looking at the transmitter because the transmitter is looking at the camera, not looking at the image of the receiver. In other words, in the prior art, both the transmitter and the receiver feel that the opposite is not looking at itself.
In order to overcome the above problem, another conventional video device assumes that a distance between the transmitter and the camera is fixed, and performs some image synthesis procedures on the transmitted image to rectify line of sight of the transmitter before transmitting the image. Please refer to FIG. 1 again. The video device A can obtain the angular deviation θ formed by a distance D1 from transmitter's eyes to the camera and a distance D2 from the transmitter's eye to a facial image of the receiver. The video device A performs an image rectification procedure on the captured face image of the transmitter, and transmits the rectified image of the transmitter to the video device B. Therefore, the receiver feels that the transmitter is looking at the receiver and therefore communications with natural eye contact are achieved.
The two above conventional video devices do not consider how the receiver uses the video device. Please refer to FIG. 1 again. The video device B is running other tasks such as document editing or programming in other windows at the same time as performing the videoconference call, and the window of the videoconference call is not in the middle of the screen. In this situation, even if the video device A already performed the image rectification process on the face image of the transmitter, the receiver still feels that line of sight of the transmitter is in direction V1, and not in direction V2. In other words, the receiver still feels that the transmitter is not looking at the receiver.
From the above, the conventional video device only takes the position of the transmitter's eyes and the position of the camera into consideration when rectifying the image of the transmitter and does not consider how the receiver uses the video device. When the videoconference window is not in the middle of the screen, the receiver can not experience natural eye interaction.